Question

people who eat lots of fruits and vegetables have lower rates of colon cancer than those who eat little of these foods. fruits and vegetables are rich in antioxidants such as vitamins a, c, and e. will taking antioxidants help prevent colon cancer? a medical experiment studied this question with 864 people who were at risk of colon cancer. the subjects were divided into four groups: daily beta - carotene, daily vitamins c and e, all three vitamins every day, or daily placebo. after four years, the researchers were surprised to find no significant difference in colon cancer among the groups.

the study is described in gina kolata,
ew study finds vitamins are not cancer preventers,\ new york times, july 21, 1994. look in the journal of the american medical association of the same date for the details.

there are some lurking variables that could explain why people who eat lots of fruits and vegetables have lower rates of colon cancer. the experiment suggests that these lurking variables or other properties of fruits and vegetables, rather than the antioxidants, may be responsible for the observed benefits of fruits and vegetables.

which of the following are the lurking variables?
□ people who eat lots of fruits and vegetables tend to get less vitamins in their diet.
□ fruits and vegetables cannot be a lurking variable because eating them is part of a normal diet.
□ fruits and vegetables contain fiber. this could account for the benefits of those foods.
□ fruits and vegetables contain sugar and fat which could affect rates of colon cancer.
□ people who eat lots of fruits and vegetables may have healthier diets overall, such as less red meat.

Explanation:

1. Analyze each option:

• Option 1: People who eat lots of fruits and vegetables tend to get less vitamins? This is incorrect as fruits/veg are rich in vitamins.
• Option 2: Claiming fruits/veg can't be a lurking variable is wrong; their other components (like fiber) could be.
• Option 3: Fiber in fruits/veg could account for benefits (not just antioxidants), so it's a lurking variable.
• Option 4: Fruits/veg are low in sugar and fat, so this is incorrect.
• Option 5: Overall healthier diet (less red meat) is a lurking variable as it's related to fruit/veg intake and colon cancer.

Answer:

• Fruits and vegetables contain fiber. This could account for the benefits of those foods.
• People who eat lots of fruits and vegetables may have healthier diets overall, such as less red meat.